The lancet is widely used in various medical units as a medical instrument for taking blood from the human body. The existing lancets can be divided into a puncture lancet and an incision lancet according to the different blood-taking methods. The puncture lancet acts on the blood-taking site by means of acupuncture, mainly used for taking blood from an adult's finger. The incision lancet acts on the blood-taking site by means of blade incision. The incision lancet feels less painful than the acupuncture lancet, and can take enough amount of blood, and therefore it is especially suitable for infants, particularly for taking blood from newborns' heels.
American patent U.S. Pat. No. 5,314,441 discloses a disposable cutting lancet assembly, i.e. an incision lancet. Such a lancet uses a blade, and realizes the blood-taking purpose by incising the blood-taking site with an incising action. The incising action is mainly performed by a supporting arm of the blade that moves along a copying track slot under the push of a spring. The supporting arm of the blade is provided with a pivot pin, which is located in the copying track slot. When the movement starts, the blade is stretched out of the casing, and performs the incising movement, and is then retracted into the casing again via a path of “water drop” form. Such an incision blood-taking mechanism is simple in structure and reliable in movement, especially suitable for taking blood from infants' heel. However, because of the combination of the supporting arm of the single blade and the copying track slot, the movement track of the point of the blade is of an arc, which is more difficult in controlling incision depth and incision width; in other words, because of limitation of the mechanism, it is very difficult to accurately obtain the incision depth within the range of 0.5˜2 mm and the incision width within the range of 2.5˜3 mm. Therefor, a problem that the present invention emphasizingly studies is how to design a new incision blood-taking mechanism, so as to meet the requirement on controlling the incision depth and the incision width.